This type of system is employed as a combination system in medical engineering for example and, as well as an electromagnetic position detection and mapping system, can feature an angiography system with a C-arm x-ray device. Medical interventions into a patient are supported by the system, with for example the instrument being navigated or guided in the patient on the basis of images of the patient obtained with the C-arm x-ray device and position data obtained with the electromagnetic position detection and mapping system of the instrument, by an image of the instrument being inserted into the images obtained with the C-arm x-ray device. For this purpose the electromagnetic position detection and mapping system and the C-arm x-ray device or the electromagnetic position detection and mapping system and the images obtained with the C-arm x-ray device generally registered with one another, so that an image of the instrument can be edited into the images.
U.S. Pat. No. 5,255,680 A for example describes a device which features an electromagnetic signal tracking system, a medical instrument able to be introduced into the body of a patient and an x-ray device. The medical instrument able to be introduced into the body of a patient comprises a coil for creating an electromagnetic field. Once the medical instrument is introduced into the body of the patient and creates the electromagnetic field, this field is detected by receive coils arranged on the x-ray device, with a tracking/display unit determining the positions of the medical instrument in the body of the patient. Furthermore during of a medical intervention into the patient fluoroscopy images of the patient into which a mark characterizing the positions of the medical instruments in the body of the patient is inserted are recorded at specific intervals.
In this way for example puncturings, general catheter application or catheter applications at the heart of a patient can be supported, in which the instrument, be it a puncturing needle or a catheter, after penetration into the patient can at least partly no longer be followed visually by eye, but must be navigated or guided in the patient with reference to the images.
Thus, in the treatment of heart arrhythmias of a patient by means of ablation an ablation catheter is introduced with the aid of x-ray images obtained with the C-arm x-ray device of the angiography system, be they 2D or 3D images, via veins or arteries into a heart chamber of the patient and the tissue causing the heart arrhythmias is removed by high-frequency current. The prerequisite for successfully carrying out a catheter ablation is on the one hand the precise pinpointing of the cause of the heart arrhythmias in the heart chamber and on the other hand the precise cauterization of the tissue causing the heart arrhythmias. The tissue concerned is pinpointed in an electrophysiological examination, in which the electrical potentials are recorded locally resolved with a mapping catheter introduced into the heart chamber. 3D mapping data of the heart chamber is obtained from this electrophysiological examination, the so-called electroanatomical mapping, for example, which can be visualized on a display device. The mapping function and the ablation function are also frequently combined in one catheter, so that the mapping catheter is simultaneously also an ablation catheter.
A known electroanatomical 3D mapping method, as is able to be performed for example with the CARTO system from Biosense Webster Inc., USA, is based on the electromagnetic principle. Transmitters arranged below a patient generally establish three, but with the systems currently being widely employed, even nine different electromagnetic fields of low intensity. By means of electromagnetic sensors integrated into the catheter tip of the mapping catheter it is then possible to measure the voltage changes within the electromagnetic fields induced by the catheter movements and, with the aid of mathematical algorithms, to compute the position of the mapping catheter at any given point in time. By scanning the contour of a heart chamber point-by-point with the mapping catheter while simultaneously detecting the electrical signals of the sensors, 3D mapping data is obtained or an electroanatomical three-dimensional map is produced in which the electrical signals can be reproduced color-coded.
The most accurate possible determination of the positions of the mapping catheter or of the ablation catheter is of decisive importance in this case for obtaining high-quality mapping data and to enable the mapping catheter or the ablation catheter to be navigated according to the actual anatomy of the patient in the body of the patient with reference to the mapping data and/or to the images obtained with the C-arm x-ray device. Inaccuracies in determining the positioning of the mapping catheter or of the ablation catheter lead in the diagnostics or the therapy, for example in the diagnostics and therapy of stimulus formation and stimulus conduction problems in the heart, to less than optimum results. Not infrequently examinations and interventions taking several hours are able to be traced back in the electrophysiological laboratory to inaccuracies in the position determination of a mapping or ablation catheter.